The overall goals of this project are to examine the functions of alveolar macrophages from a spectrum of HIV infected patients and to quantitate the level of HIV in these cells and to examine determinants of replication of HIV in alveolar macrophages and the mechanisms underlying the functional consequences of HIV infection in macrophages. Bronchoscopies are performed on the GCRC to obtain cells used in this study. One substudy is to define the natural history of lymphocytic alveolitis (LAL) in a longitudinal study of HIV-infected subjects by examining the phenotype and viral load in bronchoalveolar cells versus blood mononuclear cells and selected functions that could impact on the pathogenesis of LAL. In this longitudinal yearly analysis of 20 asymptomatic HIV-infected subjects with no previous history of pulmonary disease, subjects have 2 visits to the GCRC: one for questionnaire, CXR, and PFTs and the second at 1 or 2 weeks later for lavage and venipuncture. Ongoing cross-sectional studies of HIV infected versus healthy controls will continue.